MAIN CONCLUSIONS

The following are the main conclusions which were reached after thorough examination of the effects of the bombs dropped on Hiroshima and Nagasaki:

  1. No harmful amounts of persistent radioactivity were present after

    the explosions as determined by:

    1. Measurements of the intensity of radioactivity at the time of

      the investigation; and

    2. Failure to find any clinical evidence of persons harmed by

      persistent radioactivity.

The effects of the atomic bombs on human beings were of three main types:

  1. Burns, remarkable for (1) the great ground area over which they were

    inflicted and (2) the prevalence of "flash" burns caused by the instantaneous heat radiation.

  2. Mechanical injuries, also remarkable for the wide area in which

    suffered.

  3. Effects resulting from penetrating gamma radiation. The effects from

    radiation were due to instantaneous discharge of radiation at the moment of explosion and not to persistent radioactivity (of either fission products or other substances whose radioactivity might have been induced by proximity to the explosions).

The effects of the atomic bombs on structures and installations were of two types:

  1. Destruction caused by the great pressure from the blast; and

  2. Destruction caused by the fires, either started directly by the

    great heat radiation, or indirectly through the collapse of buildings, wiring, etc.

  1. The actual tonnage of T.N.T. which would have caused the same blast

    damage was approximately of the order of 20,000 tons.

  2. In respect to their height of burst, the bombs performed exactly

    according to design.

  3. The bombs were placed in such positions that they could not have

done more damage from any alternative bursting point in either city.

  1. The heights of burst were correctly chosen having regard to the type

    of destruction it was desired to cause.

  2. The information collected would enable a reasonably accurate

    prediction to be made of the blast damage likely to be caused in any city where an atomic explosion could be effected.